(Battery Division Student Research Award sponsored by Mercedes-Benz Research & Development) Advanced Electrochemical Energy Storage Systems: Material Development, Alternative Electrode Processes & Planar Devices

Abstract

Future advancements in energy storage systems (lithium-ion batteries/LIBs and beyond) rely on the development of novel materials, innovative electrode/device architectures and scalable processing techniques or a combination thereof. In this talk, I will discuss my work on each of these three aspects including in situ characterization of planar devices as well as the development of nanomaterials and additive-free electrode architectures via alternative manufacturing processes such as dry/cold pressing and extrusion printing, respectively. Operando studies can elucidate the reaction behavior of battery electrodes during operation; however, specialized electrochemical cells are required to study these materials in their natural environment (in situ). In this study, a planar microscale battery with an open cell configuration was designed to investigate the structural evolution and concomitant solid electrolyte interphase formation of model electrode-electrolyte systems, such as Na-MoS2.1 By coupling an atomic force microscope with the planar electrochemical cell platform, real-time topographical observations of MoS2 electrodes during sodiation are readily achieved, which leads to crucial information regarding battery operation at the nanoscale. The use of advanced in situ/operando techniques with this newly developed planar battery configuration can elucidate the electrochemical behavior of numerous electrode-electrolyte systems, particularly for alkali-metal-ion batteries, during cycling. The drive towards lighter electric vehicles with longer ranges requires the development of higher energy density systems beyond conventional LIBs, such as lithium-oxygen (Li-O2) batteries. To increase battery performance for practical applications, high mass loading electrodes are advantageous as long as optimal battery reactions are maintained throughout the entirety of the “thick” electrode. Here, I present a facile, alternative electrode processing method known as dry/cold pressing, where a highly porous and compressible carbon nanomaterial (holey graphene or hG) enables the formation of mechanically robust, high mass loading electrodes for Li-O2 batteries.2-3 Dry pressing hG, the compressible matrix, with incompressible materials also enables the preparation of unique mixed and stacked/sandwich electrode architectures under binder- and solvent-free conditions.3 The enhancements in electrochemical performance demonstrate the promise of dry pressed electrode architectures and the reported additive-free processing method for advanced electrochemical energy storage systems. Additive manufacturing (AM) techniques also show promise towards the fabrication of complex 3D designs for advanced electrochemical devices. In particular, the development of inexpensive, sustainable (aqueous), and easily processable material ink systems and the use of a facile and low-cost fabrication process, such as extrusion-based 3D printing, are advantageous for scalable battery manufacturing. In this work, hierarchically porous electrode architectures are readily extruded using additive-free, aqueous graphene oxide-based (GO) ink compositions and demonstrated as the first 3D printed Li-O2 cathodes.4 The development of a nanoporous GO material enabled trimodal porosity (nano-micro-macropores) within the 3D printed mesh architecture, which provides facile mass/ionic transport pathways and enhances active-site utilization during battery operation. The results demonstrate the potential of AM techniques towards the scalable fabrication and improvement of advanced energy storage devices through structurally conscious designs as well as tailored material compositions.